Future of neutron production lies in pulse sharing and cash

February 5, 1999

To keep leading the world in neutron technology, ISIS needs long-term investment. Judith Redfearn reports.

ISIS, Rutherford Appleton's world-leading spallation neutron source, plans to stay at the forefront. The facility is preparing bids for two major upgrades that would first increase the number of neutrons available for scattering experiments by 50 per cent and later provide cold neutrons to complement the hot neutrons it already has available.

"This improvement will give a significant payback in condensed matter science," says Colin Carlisle, head of the neutron scattering division at ISIS. It will also help maintain the UK and Europe's world lead in neutron technology and provide a stepping stone to a next generation European Spallation Source.

A bid for more than Pounds 6 million for the first upgrade is under discussion with the Engineering and Physical Sciences Research Council. "We hope this upgrade could begin this year and be completed within two years," says Carlisle.

The second upgrade is more ambitious. It would add a second target station for experiments with cold neutrons at an estimated cost of Pounds 50 million. Such a sum would overburden the UK's research councils, which have no mechanism for funding large capital projects. But hopes are now pinned on the new Pounds 600 million joint research infrastructure fund. ISIS is collaborating with universities whose academics are major users of the source to put a bid in to the fund in April.

However, it will be five years before the target station is operating. "If we look at the short term, we will never renew our capital assets," says Carlisle.

ISIS began operating in 1985. It accelerates hydrogen ions to 70 MeV before injecting them into a synchrotron, where they are stripped of their electrons and accelerated to 800 MeV.

Neutrons are produced by bombarding a heavy metal target with these 800MeV protons. The process is repeated every 50 seconds to give a pulsed source of high intensity, high energy and good resolution. ISIS is thus complementary to the high-flux neutron reactor at the Institut Laue Langevin in Grenoble, France, which produces a steady stream of neutrons at lower energies.

The first upgrade will increase the number of available neutrons by adding four extra radio frequency cavities into the synchrotron ring to reduce the number of protons lost during acceleration. "It will cost about 2 per cent a year to get 50 per cent more neutrons. This is very cost effective," says Andrew Taylor, ISIS director.

Teams in the US and Japan, which have plans for their own next generation spallation neutron sources, are collaborating on the research and development involved in designing RF cavities.

The second upgrade involves pulse sharing the enhanced beam. "If we take one pulse in five from the present source, we can direct it on to another target. We can pulse share," says Taylor.

At present cold neutrons are produced via a cold moderator in the source, but this method "ends up compromising on the production of all neutrons". The target station would have no such problems and would open up new avenues of soft condensed matter research.

The increased power and intensity will give enhanced clarity and allow measurements of real time processes. "We will be able to improve the technology that will take science further. For example, we will be able to look at real catalysts while they are catalysing reactions," says Carlisle.

A second target station would provide more capacity for new instrumentation. "Lots of people want to put more instruments on ISIS, but there's nowhere to put them," says Taylor. The plan is to move some existing instruments from the first target station on to the second, leaving some space for new leading-edge instruments on both.

Taylor sees the second target station as an important step towards designing Europe's next generation spallation source. The technical and scientific cases for the ESS are being prepared under the EU's Framework programme and by the European Science Foundation. "The ESS will have to be optimised across the board. It will also have hot and cold neutron targets," says Taylor.

The ISIS upgrade would also provide the opportunity for ESS instrument development, an area at risk of relative neglect, according to a recent Organisation for Economic Cooperation and Development report on future neutron supply and demand.

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